A chlorine gas explosion killed 12 people and injured more than 250 on Monday, authorities said, when a tank that fell from a crane released a poisonous yellow cloud at Jordan's Aqaba port.Footage on state-owned Al-Mamlaka TV showed the large cylinder, said to have been carrying about 30 tonnes of gas, plunging from a crane on a moored vessel and violently releasing the chlorine gas cloud.The force of the blast sent a truck rolling down the dock, while port workers ran for their lives.